Using Spatial Epidemiology as a Tool to Better Understand Influenza-like Illnesses by Andrea ...

156 Pages·2013·7.43 MB·English

UsingSpatialEpidemiologyas aTooltoBetterUnderstand Influenza-likeIllnesses
by
AndreaRush-Sirski
DepartmentofCommunityHealthSciences
UniversityofManitoba
AThesissubmittedtotheFacultyofGraduateStudiesof
TheUniversityofManitoba
inpartialfulfilmentoftherequirementsofthedegreeof
MASTER OFSCIENCE
Copyright©2013byAndreaRush-Sirski
Abstract
InfluenzaisapopulationhealthissueinCanada,withanannualinfectionrateof
10-25%ofthepopulation. Thepurposeofthisthesis wastoanalyzeinfluenza-like
illnesses(ILI)forthefiscalyears(April1toMarch31)from 2004-05throughto2008-
09,bothspatiallyandtemporally,throughouttheprovinceofManitoba. ILI, forthe
purposeofthis study,includeddiagnosesofpneumoniaandinfluenzaand acute
respiratoryinfectionasdeterminedbyICD-09 andICA-10codes. As withother
publishedstudiesandtheaccepteddefinitionsof ILI, repeatcaseswithinaseasonwere
included.Theanalysisusedaframeworkspecifictospatialanalysis,andincorporatedthe
principlesofpopulationhealthandecologicalframeworks. Theunderlyingobjectivesof
theresearchweretobetterunderstandthepatterns of ILIdiagnoses aswell as the
characteristicsofthosediagnosed.
Thedatawereexploredinthreeways: employingmethodsofdatavisualisation,
explorationandmodeling,withtheincorporation ofthedeterminants ofhealthtoinform
theresultsand guidethechoiceofregressionvariables. Differentmapswerecreatedto
showtheresultsfromvarious perspectivesandnegativebinomialregressionanalysis was
usedtotestwhich,ifany,ofthechosenvariables (includinghouseholddensity, co-
morbidityscore,incomequintileandage)weresignificant.
Basedonthisresearch,onecouldconcludethatalthoughclustersofILIdo exist
intheprovinceofManitoba,aclearrelationshipdoesnotexistbetweenthedeterminants
ofhealthand ILIas was expected. Althoughthe agevariable yieldedpredictableresults,
higher riskofdiagnoses amongstthehighdensityhouseholds orinthelowestincome
ii
quintileswasnotobserved. Itishoweverunclear as tohowtheseresultswereaffectedby
thelimitationsofthestudy, particularlytheinclusionofrepeatcases.
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Acknowledgements
Although Iamtheauthorofthisthesis,Ifeelconfidentsayingitwas agroup
effort. Thereweresomanypeoplewhoofferedtheirsupportinvariousways and Ican
honestlysaythateveryoneinmylifewhilecompletingthisadventuredeserves
recognition. Ithank you all.
Inparticular, Iwouldliketoacknowledge thefinancialsupport Iwas fortunateto
receivefromtheCanadianInstitutes ofHealthResearch andthe WesternRegional
TrainingCentre. Theirsupportwasnotonlymonetarybutalsoeducational,providing
mewiththeopportunitytotraveltovariousconferences and gainexposuretoother
researchers. This travel wasfurtherfacilitatedbythevarioustravelawardsIobtained
whichalsocontributedto mylearningexperience.
IwouldliketoacknowledgetheManitobaCentreforHealthPolicyforuseofdata
containedinthePopulationHealthResearchDataRepositoryunderproject #2010/2011-
06. Theresultsandconclusionsaremyownand noofficialendorsementbythe
ManitobaCentrefor HealthPolicy, ManitobaHealth,orotherdataprovidersisintended
orshouldbeinferred.
Iwouldalsoliketo acknowledgemythesiscommitteeandofferallof you a
heartfeltthank you. Eachofyouprovided mewithaverydistinctareaofexpertisethat
trulyhelpedshapemythesis. Icannotimaginehavingcompletedthisventurewithout
anyof you. Iamso gratefulto you-Alan,CarolandChris–fortheconstructive
feedbackand guidancethatyouprovidedalongtheway.
Mycommitteewasledbymyadvisor,Michelle;thisis as much your
accomplishmentasitismine. Yourencouragementandsupportwereparamountinthe
iv
completionofmydegree. Thanksto you Iwas givenopportunities totravelandtakepart
inconferencesthatIwouldhaveotherwisenothad. Youmadeagreatdifferenceinmy
developmentintheareaofCommunityHealthSciences thatwillreflecton myfuture
projectsthroughoutmycareer.
TheDepartmentofCommunityHealth Sciencesislikenoother. Iamso grateful
tomyfellowstudentsfor theirongoingsupportandmotivation. Wehavehelpedeach
otherthroughmanymomentsoffrustrationandtheoccasionaldesireto giveup.
Friendshipsandbondshavebeenformedoverweekends andeveningsofintensestudying
inordertomakeadeadline. Ilookforwardtocontinuingtointeractwithallofyouon a
professionalandpersonalbasis. Tothefaculty,Ialsosaythank you. Ireallyhave
enjoyedmytimeas aCHSstudentandwouldrecommendourprogramtoeveryone.
Though Isometimesdoubtedthatthisthesiswouldeverbefinished,myfamily
andfriendsneverdid. Whenfrustrationwouldsinkinafteralongday, you werealways
theretolistenandencouragemeto keep going;when Ineededbabysitterstofinishthe
lastdetails,youwerethere–thank you. Ilove youall. Ishareallofmy
accomplishmentswithmyhusband Danielanddaughter Emilia– youweremy
inspirationandmotivation.
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TableofContents
Abstract................................................................................................................................ii
Acknowledgements.............................................................................................................iv
TableofContents................................................................................................................vi
ListofTables...............................................................................................................viii
Listof Figures.................................................................................................................ix
ListofCopyrighted
Figures............................................................................................xi
ListofAppendices..........................................................................................................xi
Chapter1-Introduction.......................................................................................................1
Purpose.............................................................................................................................2
StudyObjectives and Hypotheses....................................................................................2
ChapterSynopsis..............................................................................................................4
Chapter1– Introduction...............................................................................................4
Chapter2–TheoreticalFrameworks...........................................................................4
Chapter3–Background and LiteratureReview..........................................................5
Chapter4– Methodsand Analysis...............................................................................5
Chapter5–Results.......................................................................................................6
Chapter6–Discussion.................................................................................................7
Chapter7–Conclusion................................................................................................7
Chapter2–TheoreticalFrameworks...................................................................................9
PopulationHealth Framework.........................................................................................9
Thedeterminantsofhealth.........................................................................................11
Ecological Framework...................................................................................................16
Spatial Framework.........................................................................................................18
Chapter3-Background and LiteratureReview................................................................19
Influenzaand Influenza-likeIllnesses............................................................................20
PandemicInfluenza........................................................................................................26
EpidemiologyofInfluenzainManitoba........................................................................27
Place,SpaceandTime...................................................................................................34
SpatialEpidemiology:DataVisualisation,DataExploration,DataModeling..............36
vi
Datavisualisation.......................................................................................................36
Dataexploration.........................................................................................................37
Datamodeling.............................................................................................................38
Chapter4-Methodsand Analysis.....................................................................................41
StudyAreaand StudyPeriod.........................................................................................41
DataSources...................................................................................................................44
StudyPopulation- InclusionCriteria.............................................................................46
StudyPopulation-ExclusionCriteria............................................................................51
Analysis..........................................................................................................................51
PreparationoftheData...................................................................................................52
Objective1–DataVisualisation....................................................................................54
Temporaldistribution.................................................................................................54
Spatialdistribution......................................................................................................55
Objective2–DataExploration......................................................................................57
Objective3–DataModeling.........................................................................................57
StudyVariables...........................................................................................................58
Chapter5-Results.............................................................................................................62
Objective1–DataVisualisation....................................................................................63
Objective2–DataExploration......................................................................................75
Objective3–DataModeling.........................................................................................78
Chapter6-Discussion.......................................................................................................86
Objective1–DataVisualisation....................................................................................87
Objective2–DataExploration......................................................................................90
Objective3–DataModeling.........................................................................................91
StudyLimitations andAssumptions..............................................................................98
Chapter7-Conclusions...................................................................................................102
Bibliography....................................................................................................................107
Appendices.......................................................................................................................116
vii
ListofTables
Table1–CDC WeekofFirstand Last LaboratoryConfirmedCasesbyStudyYear.....29
Table2-Datasetstobeused............................................................................................45
Table3- ICD-09-CMCodestobeincludedin ILIdefinition......................................47
Table4- ICD-10-CA Codestobeincludedin ILIdefinition.......................................48
Table5–PercentofStudyPopulationbySpecificICDCode.........................................49
Table6–CDCweeksusedfromeach FiscalYearofAdministrativeData.....................50
Table7– ICD–10–CACodesShowingICD–9 –CMCodeEquivalent....................53
Table8- Studyvariables includedinanalysis..................................................................60
Table9- InitialCaseDataforTotal Population...............................................................62
Table10–CaseDatafor StudyPopulationDuringInfluenzaSeason2004/2005–
2008/2009(CDC weeks 39-17)........................................................................................63
Table11–SimpleNegativeBinomialRegression Results..............................................80
Table12-MultipleNegativeBinomialRegression Results............................................82
viii
ListofFigures
Figure1- Apopulationhealthframework.......................................................................10
Figure2- Thedeterminants ofhealth...............................................................................12
Figure3- Populationhealthpyramid...............................................................................13
Figure4– Manitoba PrematureMortalityRates byHealthDistrictandNeighbourhood
Cluster...............................................................................................................................16
Figure5- Laboratoryconfirmedinfluenzacases byCDCweekbyseason.....................30
Figure6- Agedistributionoflaboratoryconfirmedinfluenzacases byseason..............31
Figure7- Agedistributionoflaboratoryconfirmedinfluenzacases for2008/2009season
...........................................................................................................................................31
Figure8- Laboratoryconfirmedinfluenzacases byregionalhealthauthoritybyseason32
Figure9- Laboratoryconfirmedinfluenzacases byseasonandserotype.......................33
Figure10- ManitobaRegionalHealthAuthorities andHealthDistricts.........................42
Figure11- WRHANeighbourhoodClusters...................................................................43
Figure12- TotalNumberof ILIin ManitobaperCDC Weekfrom2004/2005to
2008/2009.........................................................................................................................50
Figure13- TemporalandSpatialVariationofCombinedYears fortheEarlySeason...66
Figure14- TemporalandSpatialVariationofCombinedYears fortheEarly-MidSeason
...........................................................................................................................................67
Figure15- TemporalandSpatialVariationofCombinedYears fortheMidSeason.....68
Figure16- TemporalandSpatialVariationofCombinedYears fortheLateSeason.....69
Figure17- TemporalandSpatialVariationofCombinedYears oftheHealthDistricts 71
Figure18- TemporalandSpatialVariationofCombinedYears oftheNeighbourhood
Clusters.............................................................................................................................72
Figure19-CumulativeILIRates forCombinedYearsbyHealthDistrict......................73
Figure20-CumulativeILIRates forCombinedYearsbyNeighbourhood Cluster........74
Figure21- SpatialVariationofCombinedYearsfortheILISeason..............................75
Figure22- Areas ofHighand Low LikelihoodtoClusterAccordingtoSpatialScan
Statistic..............................................................................................................................77
ix
ListofCopyrightedFigures
Figure1- Apopulationhealthframework........................Error!Bookmarknotdefined.
Evans,R.,& Stoddart,G.(1990).Producinghealth,consuminghealthcare. Social
Scienceand Medicine,1347-1363.
Figure3- Populationhealthpyramid................................Error!Bookmarknotdefined.
Etches,V., Frank,J.,Di Ruggiero,E., &Manuel, D.(2006). MeasuringPopulation
Health:AReviewofIndicators.AnnualReview ofPublicHealth,27:29-55.
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